Science and technology

Air safety

Difference Engine: Up, up and away

AIR travel has never been safer. According to the International Air Transport Association (IATA), an average passenger travelling on Western-built jetliners would have to take no fewer than 5.3m flights before being involved in an accident. To put that in perspective, even the most frequent of fliers is unlikely ever to rack up more than 20,000 flights over the course of a lifetime. The accident rate for the airline industry as a whole is now so low that someone taking a flight a day could theoretically expect 14,000 years of trouble-free flying.

One often-heard claim about air travel is that it is 12 times safer than going by train and over 60 times less hazardous than travelling by car. However, such statistics are a little misleading. Air travel is only the safest mode of transport when fatalities are calculated in terms of distance travelled. If deaths are counted per unit of time travelled, trains are every bit as safe as planes, and cars only four times more hazardous. Then, again, if fatalities are computed in terms of the number of journeys taken, cars and trains are respectively three times and six times safer than planes.

Clearly, comparing the safety of one form of transport with that of another is no simple matter. Cars have many safety features built into them these days, but there is only minimal oversight of how they are maintained and operated, and how well their drivers are trained. By contrast, trains have their own tracks and signalling systems, and are reasonably well isolated from other hazards in the environment. Meanwhile, planes are manufactured to the most exacting of engineering standards, their operations heavily regulated, and their crews given extensive training.

Apart from having different safety features to start with, each type of vehicle plays a different role in the overall mix of transport. And the risk involved in each therefore depends not only on its inherent safety, but also on how the vehicle is used.

Cars, for instance, are mostly used for trips measured in tens of kilometres; trains for a few hundred kilometres; and planes for hundreds or even thousands of kilometres. A typical journey by air might be the 4,000km trip from New York to Los Angeles. A typical car ride might be the 55km from Los Angeles airport to Disneyland.

In comparing the risks inherent in two such journeys, the 70-fold difference in distance between them makes flying marginally more dangerous than driving (when the risk is measured in terms of kilometres travelled). But people do not normally drive that far. Were they to do so, though, driving from coast to coast would take at least ten times longer than flying—and would be over twice as dangerous (when measured in terms of hours in transit).

Yet, once again, like is not being compared exactly with like. The plane may have 250 passengers and crew on board, while the car may be carrying five people at most. Thus, the plane puts at least 50 times more lives at risk but has a 60 times better safety record than the car (when measured on a distance basis). For the individual, that makes flying marginally safer. But if the plane should crash, it could kill 50 times more people than a car skidding off the road.

Of course, not all crashes result in fatalities. In aviation terms, an accident can be anything from a plane being damaged in some way, to people being injured or even killed. An accident so severe that the plane is destroyed, or has to be written off, is known as a “hull-loss”.

As the amount of passenger traffic changes from year to year, the safety statistics IATA and other aviation authorities are most concerned with are the annual number of hull-losses, and accidents per million flights. Over the past year, Western-built passenger jets were involved in just 0.19 accidents per million flights—less than half the previous year’s accident rate. Meanwhile, the number of hull-losses around the world was down to five from 11 the previous year.

According to the Aviation Safety Network, an independent database in the Netherlands, there were 23 fatal airliner accidents during 2012, with some 475 people killed as a result. That compares with a ten-year average of 34 accidents and 773 fatalities—making 2012 the safest year for air travel since 1945.

For that, passengers can thank the expertise that goes into the assembly, equipment and inspection of aircraft produced by the likes of Airbus, Boeing, Bombardier and Embraer. Western-built jets and turbo-prop planes account for around 95% and 80% of global passenger fleets respectively. Of last year’s 23 fatal accidents, only three involved Western-built jets.

Apart from better instruments, more rigorous maintenance and improved training, there are other reasons for this huge improvement in aviation safety. One is the voluntary reporting arrangement that encourages flight crew and maintenance staff to pass along, without fear of recrimination, details of mistakes that could affect a plane’s safety.

Another is the success of IATA’s operational safety audit. This was set up in 2003 to roll the various overlapping safety requirements that airlines have to comply with into one global standard for operating and maintaining a fleet of aircraft. Airlines audited by IATA—two out of three commercial flights now are—have half the accident rate of non-audited carriers. As a result, hull-losses are becoming increasingly rare in many regions of the world.

The most dangerous place to fly remains Africa. Though airline safety is improving practically everywhere, it is deteriorating there—and is now nine times worse than the global average. Two of the three crashes by Western-built jets last year (one at Accra and the other at Lagos) involved unaudited African carriers.

Unaudited passenger jets operating between big African cities are worrying enough. But the real problem of flying in Africa—and also in many parts of South-East Asia and in countries that were once part of the Soviet Union—remains the ageing fleet of turbo-prop aircraft flying into small, regional airfields with inadequate air-traffic control systems, and little regulatory oversight. The most pressing need is to get more of these turbo-prop carriers to embrace IATA's auditing programme. The few that have already done so were accident-free last year.

Recently, the Wall Street Journal reported that, for the first time since the Flight Safety Foundation, a lobby group based in Alexandria, Virginia, started collecting figures on aviation safety, there were more accidents around the world involving corporate jets than passenger planes. That is something for busy executives to ponder as they climb aboard the company Gulfstream. It is also something air-safety administrations need to pay a good deal more attention to.

That aside, can the huge strides made in aviation safety over the past decade continue? Modern passenger jets are stuffed with aids that make them nigh impossible to crash. Even so, there are dark mutterings about the increasing use of carbon fibre in their construction—to save weight and reduce fuel consumption. Some experts fear such composite materials may hold unpleasant surprises—in much the way that unpredicted failures caused by metal fatigue destroyed the reputation of the de Havilland Comet, the first passenger jet to go into production, in the 1950s.

Others express concern that the cockpit automation designed to make aircraft safer may overwhelm pilots with its complexity and undiagnosed bugs. But whatever direction future safety measures take, there is now no shortage of data about accidents. As tools for analysing big data improve, airline safety is likely to evolve from being merely a reaction to past mistakes to becoming a way of predicting and preventing future ones.

I can pass on a story that may explain part of why corporate jets have a worse safety record than commercial. The pilot-in-command is so in fact, and can refuse to fly for any of a number of reasons, at his sole discretion, but weather along the route is the most common. The retired pilot I was talking to had over 30,000 hours of corporate flight time - an expert by any standard. He told me of a CEO in Florida with his family, who WAS going to fly back to New York NOW. But there were icing conditions on the way, and my pilot friend refused to go. Of course, he was fired on the spot, but finding another pilot immediately was impossible. Shortly thereafter, when her husband was out of earshot, the CEO's wife thanked the pilot profusely for refusing to put her, her children, and even her foolish husband at risk of their lives.
Which begs the question. How many corporate pilots swallow their better judgement to appease the boss?

As a non-pilot and non-sailor, I have no idea how long a nautical mile is (although I do know it is longer than a regular mile). Since the Economist is printed for the general public, it ought to express distance in units the general public understands. Besides, 7 - 0.3 billion people understand SI. Only 0.3 billion use the abomination that is the imperial system.

Yes - but only if commercial airplanes continue to be made by Boeing, Airbus, Embraer, and Bombardier. Otherwise the answer is "No" if Russian, Chinese, and other manufactures start producing commercial air craft as well.

You are aware, I trust, that by law the metric system is the legal standard in the US. Miles, gallons, etc. are all legally defined in terms of their metric equivalents -- have been for over a century. And Federal government agencies have, for decades, been under a legal requirement to use metric measures.

One's safest air travel experience will always be found by stepping onto a scheduled airliner which does the same route every single day, being flown by a pilot/s who does the same route in that same aircraft every single day, backed up and guided by the same air traffic controllers who track that same aircraft, and pilot, every single day, as well as the same mechanics who maintain that same aircraft every single day. The continuous and cumulative learning curve travel of these participants has the effect of steadily reducing risk. Similarly, the enormous economic stakes for commercial aircraft companies to deliver aircraft which have the safest possible records, also contributes to air safety.

Traveling via private aircraft, including corporate jets, and self-piloted aircraft of any type, cannot ever come close to the above risk-reducing effects, and as such, account for an enormous percentage of aircraft accidents, mishaps and deaths.

One of the most effective ways to shorten one's expected lifespan is to purchase and pilot one's own private aircraft -- or get into a private aircraft piloted by another.

This idea has been put forth many times before, but building large passenger planes tough enough to survive a landing on water is impractical with present technology and materials. Not impossible, mind you, for the biggest plane ever was a seaplane, but vastly inefficient.

In fact, a wide-body airliner has never made a succesful (survivable) water landing, which lead to questions whether life jackets should be put on such planes at all (in this very paper, a few years ago).

This would end flying for most people. The increased weight of hauling around a boat hull would cut into the payload too much. That being said most aircraft actually are designed to land in water and not break up, provided the water is cooperating. Ten foot swells are much harder to deal with a smooth surface.
And the statement about that US airways flight being the only survivable water landing is not accurate. The most successful yes, not surprising since from what I know Airbus builds their planes with the ability to seal up all the valves in the fuselage so that it's less leaky.
Garuda Indonesia Flight 421
1 dead out of 60 occupants
ALM Flight 980
23 dead out of 63, and a good number of the pacs did not have their seat belts secured at the time.
Pan Am Flight 6
No dead out of 31
Ethiopian Airlines Flight 961
125 dead out of 175. Hijacked and ran out of fuel. With no engines the aircraft lacked sufficient power to operate flaps, which in turn forced it to attempt to ditch at a much higher speed than is a good idea.
There have been other ditchings of wide body's of course, with no survivors.
South African Airways Flight 295
Asiana Airlines Flight 991
They both had fire's on board at the time, which probably, certainly in the case of Asiania Flight 991, had damaged the hydraulic systems of the aircraft making control difficult.
There have been other cases of airplanes crashing in the sea, but I've only included cases were the crew would be trying to land in water. Uncontrolled nose dives, yeah no way you are going to survive that.
I included links about the crashes originally, but they triggered the spam filter.

It's a byproduct of progress as we would all agree it is. Anaesthetics surely had much to do with the abolition of corporal punishment as our expectation of being subjected to severe pain declined. With families now rarely more than two children we express the same horror at the modest level of casualties in Iraq (not including civilians) as we used to when more than 10 times as many US soldiers were killed in Vietnam. Let alone WW1 or WW2's Eastern front....

And I shall be thoroughly put out if my enjoyable life doesn't extend healthily into my 90s!

In the 12 years from 2000 through 2011 the US lost about 475,000 lives on the roads (at early 1970s rates this would have been around 600,000).

Curiously, this doesn't seem to have much impact on the public imagination, certainly not compared to the reactions ranging from fear to hysteria with respect to the risk from air travel and terrorism, even though the death toll due to these causes is lower by a couple orders of magnitude.

To the contrary.
Cross winds are the biggest danger for landing, departing, and taxiing aircraft. Especially in the case of taxiing, bigger is better in this context. It is harder for the plane to get blown over. I was on a dinky turbo-prop one time and we had to land at almost double the normal speed because the crosswinds were so bad. (Remember, Newton's Second Law.) Bigger engines are also less susceptible to catastrophic damage from bird strike.

Really? An increase in airplane safety leads you to conclude we are retuning to our savage roots?
If we are getting more and more worried about personal safety, perhaps its becasue our lives are becoming more and more valuable.

You can decompression in an aircraft without crashing the aircraft - the most famous case actually happens many years ago in Hawaii where the roof of the aicraft was partially gone, people got sucked out, but the aircraft landed. A recent case was a hole got blown out from HK to Australia flight, and again the plane landed safely.

There were people didn't wear seat belts during a (very) bumpy ride, got their head smashed into the baggage component, and died. And planes are designed to survive (very) bumpy rides without crashing.

At the same time, the plane can have hull loses without fatalities as well.

Flight miles are measured in nautical miles in the vast majority of the world's airspace. Kindly don't pander to those ignorant of anything but the metric system when writing articles such as this. To do so when referring to flight in the USA is especially ludicrous.